cannot read/write sparse matrices to matlab v4

[David Bateman]

Daniel Heiserer wrote:
> Hi,
>
> the read and write of sparse matrices to v4 matlab does not work:
>
> octave:5> tic;load C4.mat;toc
> error: load: can't read sparse matrices
>
>
> When writing is tried, it seems octave will internally create a full matrix before writing it to the v4 file. This will explode once the matrix is too large:
>
>
> N=1E7;C=sparse(ceil(N*rand(N,1)),ceil(N*rand(N,1)),rand(N,1),N,N);
> save -v4 C4.mat C
>
>
> octave version was:
>
> octave:5> version
> ans = 3.0.0
>
>
>   
Huh, I never even realized that matlab could save a sparse matrix to a
v4 file format! The documentation has a flag for the sparse file format
but then doesn't document how the nnz, cidx, ridx and data parts of the
Sparse matrix are stored. So I presumed that as documented they were
saved as full matrices in v4 format. Without knowledge of the v4 sparse
format I'm not really sure how to implement this..

D.

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David Bateman                                David.Bateman at motorola.com
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